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Ambient air pollution exposures and risk of rheumatoid arthritis: results from the Swedish EIRA case–control study
  1. Jaime E Hart1,2,
  2. Henrik Källberg3,
  3. Francine Laden1,2,4,
  4. Tom Bellander3,
  5. Karen H Costenbader5,
  6. Marie Holmqvist3,
  7. Lars Klareskog3,
  8. Lars Alfredsson3,
  9. Elizabeth W Karlson5
  1. 1Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  2. 2Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA
  3. 3Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
  4. 4Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
  5. 5Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  1. Correspondence to Dr Jaime E Hart, Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA; Jaime.hart{at}


Objective Environmental factors may play a role in the development of rheumatoid arthritis (RA). We examined whether long-term exposures to air pollution were associated with the risk of RA in the Swedish Epidemiological Investigation of Rheumatoid Arthritis Study.

Methods We studied 1497 incident RA cases and 2536 controls. Local levels of particulate matter (PM10) and gaseous pollutants (sulphur dioxide (SO2) and nitrogen dioxide (NO2)) from traffic and home heating were predicted for all residential addresses. We examined the association of an IQR increase (2 µg/m3 for PM10, 8 µg/m3 for SO2 and 9 µg/m3 for NO2) in each pollutant at different time points before symptom onset and average exposure with the risk of all RA and the risk of the rheumatoid factor and anti-citrullinated protein antibody (ACPA) RA phenotypes.

Results There was no evidence of an increased risk of RA with PM10. Total RA risks were modestly elevated for the gaseous pollutants, but were not statistically significant after adjustment for smoking and education (OR 1.18, 95% CI 0.97 to 1.43 and OR 1.09, 95% CI 0.99 to 1.19 for SO2 and NO2 in the 10th year before onset). Stronger elevated risks were observed for individuals with less than a university education and with the ACPA-negative RA phenotype.

Conclusions No consistent overall associations between air pollution in the Stockholm area and the risk of RA were observed. However, there was a suggestion of increased risks of RA incidence with increases in NO2 from local traffic and SO2 from home heating sources with stronger associations for the ACPA-negative phenotype.

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  • LA and EWK contributed equally to the manuscript.

  • Funding This study was supported by NIH grants AR047782 and AR052403, the Swedish Medical Research Council, Swedish Council for Working Life and Social Research, Swedish Medical Research Council, the insurance company AFA, FAMRI (Flight Attendant Medical Research Institute), and the COMBINE (Controlling Chronic Inflammatory Diseases with Combined Efforts) project.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval All aspects of the study were approved by the ethics committee of Karolinska Institutet.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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